In the art of printing machines for securities having the form of notes, such as banknotes, checks and other similar objects, an important feature which is printed on said objects is a serial number. For example, each banknote printed on a substrate, such as a sheet of paper, receives a unique combination of numbers and characters building the serial number of said note.
Many numbering processes have been developed in the art. For example, U.S. Pat. No. 4,677,910, the content of which is incorporated by reference in the present application, discloses a process and an apparatus for processing security paper prints arranged in lines and columns on a carrier in the form of paper webs or sheets. The print carriers pass, in succession, by a reading instrument which detects the positions of the defective notes identified by a mark and feeds the position to a computer for storage, a cancellation printer controlled by the computer which provides the defective notes with a cancellation print, and a numbering machine. The numbering mechanisms of this numbering machine are moved forward by the computer in such a way that always the satisfactory paper prints, placed in succession in any longitudinal row, are serially numbered, the spoilt notes being neglected. Subsequently, the printed carriers, having passed by another reading instrument, are cut into individual security papers or notes, the defective notes are separated out in a separation device and the remaining, serially numbered individual security notes are assembled to form bundles, each having a complete numerical sequence. In this way, a correct and complete numerical sequence of the security notes in the bundles is ensured, in spite of the separation of defective notes.
With securities usually printed in matrix format on a substrate, several problems arise when one wants to build packs of individual securities which are numbered with successive numbers. A first problem is due to the fact that each sheet of substrate has to be cut into individual notes. In order to maintain a proper production speed, it is in principle not possible to cut each note individually of each produced sheet of substrate, but preferably a run of sheets are piled up and cut together by appropriate cutting devices known in the art.
It has also been determined that a good compromise has been attained by working with piles of 100 sheets of substrate since this is an optimum size to be cut in a precise manner when the piled sheets are to be cut into individual notes.
Another problem one is faced with is the individual numbering of each produced object, such as security note. It is of course not possible to number each produced note once it has been cut with consecutive numbers until the completion of a so-called close set of numbers, usually comprising a million numbered notes in a particular series. Actually, the notes are numbered before being cut, i.e. when the sheet of substrate is still complete, the numbering being part of the printing process of the notes, rather than being carried out after the cutting operation. According to this method, another parameter that must be taken into account is the presence of misprints or defective notes on the substrate. Since all notes of the packs of notes are numbered consecutively, it is not reasonable to build packs of notes with defective notes, which have to be replaced later by correct notes with the same serial number. U.S. Pat. No. 4,677,910 discloses a solution to this problem, as indicated here above. In this patent however, the sheets of substrate are cut individually into individual notes: because of the presence of misprints, it is not possible to cut piles of sheets into piles of individual notes and the individual notes must be sorted out before being piled up to form bundles of notes with consecutive numerical sequences.
According to another process, the sheets comprising misprints are removed before the numbering operation and only sheets with no defective notes are numbered.
Another numbering process is disclosed in European patent application EP 0 598 679, the content of which is enclosed by reference in the present application. In this process, for each sheet comprising N impressions of notes arranged in transverse and longitudinal rows which is run through a numbering machine with N numbering units, the numbering comprising a closed set of numbers with W notes of value and the number of sheets amounting to a multiple of 100, the number of note prints N is divisible by 10 and on each sheet every 10 neighbouring note prints form a group of ten, which receive numbers of the same series of a thousand. Further, in each sequence of 100 successive sheets, the note prints lying respectively at the same note position, that is to say in the same transverse row and in the same longitudinal row, are numbered with the 100 successive numbers of a particular series of a hundred, and the ten note prints of a group of ten of each sheet are numbered with numbers of successive series of hundreds with the same ones and tens. Moreover, the note prints on all subsequent sequences of 100 sheets each are numbered with numbers of successive series of thousands with in each case the same ones, tens and hundreds for the note prints lying at the same note positions, so that the note prints of a sequence of 100 sheets belonging to one and the same group of ten receive the complete sequence of number of a particular series of thousand and the note prints of the following sequence of 100 sheets belonging to the same group of ten receive the complete sequence of numbers of the following series of a thousand, the note prints belonging to various groups of ten being numbered in such a way that the numbers of one group of ten differ from the numbers of another group of ten by an amount which is at least equal to W/Z, Z being the number of groups of ten of a sheet.
Another technical field which is involved in the process of numbering prints or objects arranged in lines and columns on a substrate is of course the numbering devices used to print the proper number on each individual note print. Two main categories exist for such devices, which usually comprise several numbering wheels or disks having the successive numbers or characters engraved in raised form on their circumference. The numbering wheels are either sequentially actuated, which means that such a numbering device is only able to print successive numbers, the wheels being displaced by one step in a fixed sequence, or freely actuated numbering wheels which are able to take any position in an independent fashion, thus being able to print any desired sequence of numbers.
The first category of numbering devices uses a simple mechanism which is only able to change numbers in a sequential order. The numbering wheel for the ones is mechanically coupled to the numbering wheel for the tens, so that the tens wheel is moved one step forward only when the ones wheel passes from the number 9 to the number 0. Similarly, the wheel for the hundreds moved one step forward only when the tens wheel and the ones wheel passes from the number 99 to the number 00 and so on. Such a numbering device is therefore unable to either skip a number or print any given number successively and only strict consecutive numbering processes may be carried out with this numbering device. These devices are known in the art, for example from U.S. Pat. No. 4,677,910.
The second category of numbering devices with freely adjustable numbering wheels is disclosed in U.S. Pat. No. 5,660,106, the content of which is incorporated by reference in the present application. This patent discloses numbering devices using an electromagnetic system to block the numbering wheels in the desired position for each numbering step of printed matter. Therefore, the disclosed fully automatically settable numbering unit has the advantage that selectively arbitrary, even non-sequential, numbers can be set at any time, allowing a skip of numbers in a sequence. For a detailed explanation of the functioning of these numbering units, reference is made to the entire disclosure of U.S. Pat. No. 5,660,106.
Such numbering devices are particularly useful in processes where numbers are skipped between notes numbered by the same numbering device or when the same number has to be printed on two or more successive notes. However, these numbering units also have the disadvantage that they are complicated with respect to sequential numbering devices, which are usually purely mechanical and also in that they become very warm due to their construction, according to which excessive amounts of energy are dissipated by friction.
Another category of hybrid numbering devices is for example disclosed in U.S. Pat. No. 4,677,910, mainly in FIGS. 6 and 6a, the corresponding description of these numbering devices being incorporated by reference in the present application. This numbering device overcomes the limitation of purely sequential numbering devices and allows changes in the sequence of numbers. The numbering device disclosed in this patent comprises six numbering wheels (see for example in FIG. 6a), i.e. from the right to the left, a wheel 21 for the ones digit, a wheel 22 for the tens digit, a wheel 23 for the hundreds digit, a wheel 24 for the thousands digit etc. All the wheels are mechanically coupled together to provide a pure sequential numbering, except for the wheel printing the ones digit which is kinematically independent from the others and moved by an electric motor. Due to the numbering process used in this patent, according to which notes which are printed on a substrate and arranged in a matrix made of lines and columns are numbered with consecutive numbers on the same sheet. Therefore, if a misprint is present on the sheet, two neighbouring notes, the misprinted one and the next note, receive the same serial number, the ones digit does not change. It is therefore necessary to skip one unit in the numbering process, that is to avoid to move the wheel corresponding to the ones digit. For this reason, this wheel is driven in an independent manner by a motor and is not moved when misprints are encountered during the numbering operation of a sheet.
There is therefore a need for simplified numbering processes and devices which are effective with respect to the different problems encountered in the field of numbering objects arranged in lines and columns on a substrate, i.e. the size of the substrate or piled substrate, the numbering process used to optimise the numbering operations and the numbering devices able to carry out the desired numbering process.